A memory unit is defined as “nonvolatile”if no inside data is lost after disconnection of the power supply. Therefore, the nonvolatile memory plays a very important role in both the computer and the telecommunication industries. This is especially true of the flash memory, which is one of the hot products in today's nonvolatile memory market.
However, the nonvolatile flash memory is intrinsically limited with respect to operation times because the inside memory cells must be refreshed based on the principle of hot-carriers field effect, as a result of which inside data thereof must be erased and rewritten with 1s instead of previously existed 0s and is before writing new data. During writing, because the required operational voltage is 7V or higher the oxidation layer in the flash memory may be impaired to some extent by repeatedly writing and erasing operations that would undoubtedly shorten its lifetime,
For improving the above said defect, only a few protective measures are available so far, such as employing arithmetic to uniformly use every block in the flash memory and thereby potentially prolong the lifetime of the memory by as long as one million times. This known effect may be enhanced when associated with the present invention.